Gas reaction rotors



-Jan.,12, 1960 'F[ R. GOLDSCHMIED 2,920,813

GAS REACTION ROTORS Filed Jan. 2, 195a COMPRESSED AIR SOURCE FABIO R. GOLDSCHMIED INVENTOR ATTORNEY United States PatentC c 1 GAS REACTION ROTORS Fablo R. Goldscbmied, West Roxbury, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 2, 1958, Serial No. 706,653

1 Claim. (Cl. 230-134) This invention relates to gas reaction rotors, and relates more particularly to the rotors of centrifugal fans.

In the co-pending application of John E. McDonald, Serial No. 627,459, filed December 10, 1956, there is disclosed a method of increasing the gas pressure from a centrifugal fan by blowing gas such as air, from the interiors of airfoil blades forwardly through slots in the driving faces of the blades adjacent to the trailing edges of the blades, at substantial angles to the chord lines of the blades. This method has several important advantages. It enables a small, less expensive rotor to provide the same increase in gas pressure that a larger, more expensive rotor has previously provided. It enables a rotor designed for normal loads to easily handle peak loads. It also provides an effective volume control since the flow of air out of the slots can be varied for varying the pressure increase provided by a fan.

My invention is an improvement over the one disclosed in said application in that I provide the fan blades between the trailing ends of their driving and trailing faces with peripheral faces in which the air discharge slots are placed, the inner surfaces of the driving and trailing faces being curved to cause the air jets to be discharged forwardly in the direction of rotation past the trailing ends of the driving faces. This provides a more rugged blade construction with wider jet slots and wider air passages leading to the slots.

An object of this invention is to improve airfoil blades used in gas reaction rotors and from which gas under pressure is projected for improving the performances of the rotors.

Another object of this invention is to provide an airfoil blade for a gas reaction rotor with a blunt instead of a sharp trailing edge, and to project gas under pressure from within the blade, forwardly through a slot in the blunt trailing edge for improving the performance of the rotor.

This invention will now be described with reference to the annexed drawings, of which:

Fig. 1 is an end elevation of a double-inlet, centrifugal fan rotor embodying this invention, a portion of the adjacent front plate being removed, and several blades and the fan shaft shown in section;

Fig. 2 is a side elevation of the rotor of Fig. 1, and shows also a source of compressed air connected through passages in the rotor to the interiors of the blades, and

Fig. 3 is an enlarged sectional view of one of the fan blades.

The fan rotor has a center plate and front or side plates 11 with airfoil blades 12 supported between the center plate 10 and each side plate 11. The side plates 11 have the usual axial inlet openings 13. The center plate 10 is attached by supports 14 to a rotary shaft 15.

Patented Jan. 12, 1960 The shaft 15 has a central air passage 16 which extends through a seal 17, and is connected through a valve 18 and tubing 19 to a compressed air source 20. The valve 18 has an adjusting handle 21 with an indicator 22 on one end, the indicator 22 being opposite a scale 23 calibrated in terms of volume or pressure.

The center plate 10 has an opening 25 around the passage 16 into which the passage 16 discharges through a slot 26. Radial passages 28 in the center plate 10 connect with the opening 25 and with transverse passages 29 which line up with the hollow interiors of'the blades 12.

The blades 12 instead of having the usual sharp trailing edges, have between the trailing ends of their driving faces 30 and their longer trailing faces 31, forwardly (counter-clockwise in the direction of rotation) inclined peripheral faces 32 through which extend forwardly curved jet slots 33. The inner surface of each driving face 30 has an inwardly extending, curved bulge 34 forming one side of a slot 33 and providing a constriction for increasing the velocity of the air supplied through a slot 33.

When the valve 18 is opened, compressed air is supplied from the source 20 through the passage 16, slot 26, opening 25 and passages 28 and 29 into the hollow interiors 35 of the blades, and from the blades through the slots 33. The slots 33 are arranged to discharge jets of air outwardly and forwardly past the driving faces 30 of the blades.

With the rotor rotating in a counter-clockwise direction as shown by the arrow of Fig. 1, the jets of air projected from the slots 33 can increase the pressure added to the gas upon which the rotor works by as much as 40% more than is provided with the air jets shut off. The percentage of pressure increase can be varied by adjustment of the valve 18. i

The air jets projected from the blades do not maintain boundary layer flow. On the contrary, they greatly disturb boundary layer flow, and act somewhat as flaps,

but without the mass of flaps and their mechanical problems of adjustment, and not being acted upon by the tremendous centrifugal force to which hinged physical fiaps would be subjected if used on centrifugal fan blades.

In the annexed claim backwardly curved airfoil blades are defined as airfoil blades having convex gas impacting or driving faces, having leading edges or. noses which first impact the gas handled by the blades, and having trailing ends which are downstream with respect to gas flow of their noses.

The center plate of a double inlet fan, is, of course, the back plate of each fan section, and corresponds to the back plate of a fan having but a single rotor section. Therefore, the term back plate as used in the annexed claim should be considered as a center plate where the fan involved is a double inlet fan.

What I claim is:

A centrifugal fan rotor having a side plate and a back plate, a plurality of backwardly curved airfoil blades supported between said plates, said side plate having an axial inlet opening, the noses of said blades being located adjacent the edge of said opening, the trailing faces of said blades being longer than their driving faces, said blades having forwardly inclined peripheral faces between the trailing ends of their driving and trailing faces, said peripheral faces being located adjacent the periphery of said rotor, said peripheral faces having slots therein, said blades having means within their interiors forming 3 passages connected-"to saidv slots, and means-for supplying compressed gas into said passages and out said slots, said passages being forwardly curved where they connect with said slots.

References Cited in the file of this patent UNITED STATES PATENTS 390,508 Mosher et Oct. 2, 1888 S'talker' Dec. 15, 1942 Stalker July 12, 1949 FOREIGN PATENTS Great Britain Mar. 14, 1949 Great Britain May 18, 1955 Great Britain Oct. 10, 1956 France a Nov. 28, 1938 

